On 31 October 1934, the French Ministry of Air issued a specification for a heavy fighter.[2] The specification demanded the aircraft be capable of performing three principle roles: fighter direction, in which it was required to lead formations of single-engine fighters with sufficient maneuverability, day attack, in which the type was also to escort friendly close air support and bomber aircraft, and nightfighter operations.[2] Specified performance details included a maximum speed of 450 km/h at 4,000 meters, a 300 km/h cruising speed, and an endurance of at least four hours. Armament requirements included two fixed forward-firing 20 mm cannons and a single machine gun to the rear for self defence.[2] The sought aircraft was also required to accommodate two/three seats along with a twin-engine configuration; however, some of the performance limitations imposed upon the aircraft, such as the maximum weight, served to restricted the range of suitable engines to power the type.[2]

The original Potez 630 was developed to meet this specification; two variants of the aircraft were originally submitted for considerable, one (the 630) powered by Hispano-Suiza 14AAradial engines and the other (the 631) with Gnome-Rhône 14N.[2] Other companies also produced submissions in response, including Breguet Aviation, Hanriot, Chantiers aéronavals Étienne Romano, and Loire-Nieuport. Each of the competing manufacturers were requested to produce a single prototype for evaluation at their own expense; work on the first prototype, designated as the Potez 630-01, commenced in April 1935.[2] In addition to the Potez 630, the same specification had ultimately resulted in the successful Breguet 690 series of attack aircraft.

On 25 April 1936, the Potez 630-01, equipped with a pair of 580 hp Hispano-Suiza 14, conducted its maiden flight from Méaulte, Picardy.[2] Initially, the prototype was equipped with an experimental feature in the form of a braced horizontal stabilizer that incorporated no dihedreal. On 6 May 1936, the prototype suffered some damage due to a hard landing following the mid-air loss of a propeller blade.[2] On 3 August 1936, after receiving repairs, the Potez 630-01 was transferred to Villacoublay Air Base, Île-de-France; it was soon refitted with an alternative tail arrangement similar to later production aircraft and long-stroke landing gear. On 20 November 1936, flight testing of the prototype resumed; it was shortly thereafter delivered to the Centre d'Essais de Matériels Aériens (CEMA) for official tests.[2]

The original engines of the Potez 630-01 were progressively replaced with improved models of Hispano-Suiza engine, gradually increasing thrust to reach 700 hp on takeoff.[2] At its maximum takeoff weight of 3,850 kg, the prototype was capable of a maximum speed of 460 km/h and a maximum range of 1,300 km when flown at an economical cruising speed of 300 km/h. In March 1937, the second prototype, designated Potez 630-02, performed its maiden flight from Méaulte.[3] The Potez 631-01 was damaged after a landing with its landing gear not being locked into the down position; after repairs, it was handed over to CEMA for official trials in November 1937.[4]

On 23 December 1936, the Société nationale des constructions aéronautiques du Nor (SNCAN) was officially formed, grouping together five aircraft factories; further amalgamations into SNCAN shortly took place, including Potez in early 1937.[2] Shortly following its establishment, SNCAN received a provisional order letter for 10 experimental aircraft, four of these were derived from the Potez 630, three from the Potez 631 (one being the existing 631-01 prototype), two Potez 633 light bombers and one Potez 637 aerial reconnaissance aircraft; this was promptly confirmed by a contract, under which one Potez 633 was replaced by a single Potez 637 low level ground attack aircraft.[4]

In June 1937, a letter of order for an initial production batch of 10 two-seat and 30 three-seat Potez 631 day fighters was received, the first five of which were to be delivered by February 1938.[4] As large-scale manufacturing of the Gnome-Rhône 14M engines had yet to be achieved and thus were not able to reach the desired production rate of the Potez 630, an additional order was placed for 80 aircraft powered by the alternative Hispano-Suiza engine.[4] The first 48 aircraft to be produced were equipped with Hispano-Suiza 14AB02/03 engines, these were succeeded on later models by the improved Hispano-Suiza 14AB10/11. In December 1937, regular contracts took the place of the provisional letters; a further order for 50 Potez 633 light bombers was also received, bringing the total orders for the type to 180, including the ten prototypes that had been ordered.[4]

During the late 1930s, the Potez 630 reportedly received considerable foreign interest; in addition to France, many countries were in the process of reequipping their air forces at the time.[4] One such foreign venture was the acquisition of a licence to manufacture by the Czechoslovakian aircraft firm Avia to produce a variant of the aircraft, designated as the Potez 636; none were completed prior to Czechoslovakia's annexation by Nazi Germany in 1938.[4] In 1938, a further fifty additional Potez 631s were ordered, of which 20 were to be diverted to Finland, although they never reached that country. A number of firm foreign orders was placed with SNCAN for the type, the Republic of China ordered four Potez 631 and five Potez 633, the Kingdom of Yugoslavia ordered two Potez 630 and one Potez 631, the Kingdom of Romania ordered 20 Potez 633, the Kingdom of Greece ordered 24 Potez 633, and Switzerland ordered one Potez 630 and one Potez 633.[4]

In May 1937, series production of the Potez 630 commenced.[4] Manufacturing work on the aircraft's various sections and components was shared out across various SNCAN facilities; the fuselage and tailplanes were produced were built in Caudebec-en-Caux, Normandy, the wings were made at Le Havre, Normandy, and final assembly was initially performed at Méaulte; the assembly work was later transferred to Les Mureaux.[5] In February 1938, the first production Potez 630 conducted its maiden flight; on 23 February 1938, the French Air Force accepted their first production 630 aircraft.[6] Early on, production of the Potez 630 was negatively impacted by a considerable delays, caused by a shortage of engines, propellers, and cannons; the first batch of Potez 630s were armed with four machine guns instead of the standard two 20 mm Hispano-Suiza cannons. On 2 August 1938, the first Potez 631 was officially accepted.[6]

On 15 Match 1938, a major re-equipment and expansion program of the French Air Force, known as Plan V, was approved.[6] While there had been intentions to order a more capable twin-engine aircraft, these were not ready for production, thus the Potez 631 and 633 were retained for this production program, which first involved 207 twin-engined day-and-night fighters along with 449 daytime light bombers. On 25 Match 1938, the Potez 633 was increased to 125 bombers, which were also requested to be three-seaters.[6] The Potez 633 orders were subsequently cancelled, ordering additional Potez 631 aircraft in their place; further orders of the Potez 631 were placed also to allow for the speedy withdrawal of the troublesome Potez 630.[6] Between January and June 1940, an average rate of 100 aircraft per month was maintained.[7]

The Potez 630 was a twin engine, monoplane, fully metallic three-seater with efficient aerodynamic lines and twin tailplanes. The basic design allowed for the type to replace various obsolete aircraft in the French Air Force in a wide range of roles.[7] The long glasshouse housed a crew of three, comprising a pilot, an observer or commander who was carried based upon mission requirements, and a rear gunner who manned a single flexible light machine gun. The Potez 637 featured a glazed gondola located beneath the fuselage for an observer to be carried in the prone position.[4] Some variants, such as the Potez 631 and 633, had a vertical bomb bay located between the two crew members.[4] The 630 was a relatively simple and sound design, requiring an average of 7,500 man-hours to assemble each aircraft.[7]

All members of the family (with the possible exception of the Potez 63.11) shared pleasant flying characteristics and were designed to allow for easy maintenance.

As a daytime fighter aircraft, the Potez 631 C3, its performance was relatively disappointing, partially due to a low maximum speed and inadequate rate of climb compared with contemporary fighter aircraft.[7] When applied to the nightfighter role, their lack of detection capability against enemy aircraft rendered their presence mainly ineffective.[7] Later models had a heavy armament (12 machine guns for the Potez 63.11). Unfortunately the Potez 63 family, like many French aircraft of the time, simply did not have sufficiently powerful engines to endow them with an adequate performance and they proved vulnerable to Messerschmitt Bf 109s, like the contemporary Fairey Battle and Bristol Blenheim bombers. Their similarity to the Messerschmitt Bf 110, both being equipped with twin engines, twin fins and a long greenhouse canopy, is believed to have resulted in several aircraft being lost to "friendly fire".[7]

From May 1938, production Potez 630 fighters started to be delivered; the first improved Potez 631 aircraft were received in August that year.[6] Potez 630 and 631s, in two-seater configuration, were soon used to replace obsolete ANF Les Mureaux 113 used as night fighters, while single-seat fighter groups received a number of three seat Potez 63s to act as "command aircraft", from which formations of single-seat fighters would be directed and co-ordinated by radio.[8][9] In July 1938, the first 15 Potez 630 aircraft participated in the Villacoublay Air Show.[6]

In May 1938, the Armée de l'Air (French Air Force) placed an order for 125 Potez 633 light bombers in May 1938, additional orders had also being placed by Romania and Greece for 20 and 24 Potez 633s respectively.[10] France cancelled its order for Potez 633s in the summer of 1938, but further orders for the 633 were placed by Romania (for 20 more aircraft, which had been part built under the French order), and from China, for nine. Deliveries to Romania started late in 1938, with the Greeks receiving their first aircraft in the spring of 1939. In August 1939, with the risk of war increasing the French government requisitioned 32 Potez 633s from the Greek and Romanian orders that were still in France awaiting delivery.[11]

By September 1938, the Potez 630 had begun to supplant the obsolete Bloch MB.200 bomber in the fighter direction role; however, the Potez 630's engines proved so troublesome in service that most units were rapidly re-equipped with the Potez 631 prior to the outbreak of the Second World War.[6] By 1 April 1939, a total of 77 Potez 630 and 88 Potez 631 aircraft had been accepted by the French Air Force. The retirement of other obsolete French aircraft, such as the Morane-Saulnier M.S.225 and Dewoitine D.510, could be accommodated for by the increasing numbers of Potez 631s.[12] Just prior to the outbreak of the Second World War, the French Air Force had 85 Potez 630s, 206 Potez 631s, 22 Potez 633s, 63 Potez 633s, and 5 Potez 63.11 aircraft.[13]

The Potez 633 aircraft that were exported to Greece and Romania saw greater service than their French counterparts despite their limited numbers. Greece had nine Potez 633s in service when Italy invaded Greece in October 1940. These were used for bombing attacks against Italian supply lines until shortage of spares forced their withdrawal. In June 1941, Romania joined Germany in the invasion of the Soviet Union. Two squadrons were equipped with the Potez 633 which were used to support the Romanian army as it advanced towards Odessa. In 1942, they were ultimately replaced by Junkers Ju 88 bombers, allowing the survivors to be transferred to the advanced training role.[14]

On 28 August 1939, the French Air Force initiated the mobilisation of its units, including those equipped with the Potez 630 series.[13] Due to requests from the French Naval Aviation some Potez 631 aircraft were soon diverted to replace their Dewoitine D.371 fighters. In February 1940, a new war plan, Plan V bis, was adopted; under this plan, nearly all Potez 630 and a number of Potez 631 aircraft were retired from front line service, some of these 630s were converted to become dual-control training aircraft.[13] That same month, it was decided to rearm the majority of Potez 631s, replacing their original armament of one cannon and one machine gun with two cannons and four underwing machine guns for the purpose of conducting ground attack missions; however, progress on this program was relatively slow.[15]

The French Air Force found a use for the Potez 633 aircraft as conversion trainers for units that had received the Breguet 691 attack aircraft. On 20 May 1940, three Potez 633s took part in a strafing mission against German troops near Arras. This was the types only operational mission over France as two days later the aircraft was withdrawn from front-line service.[16] A small number of Potez 633 originally destined for China were commandeered by the French colonial administration in Indo-China and saw limited action in the brief French-Thai War in early 1941.

Once active combat had begun, the Potez 631 had quickly proved to be an ineffectual interceptor; it was slower than some German bomber aircraft and 130 km/h slower than the Messerschmitt Bf 109E fighter. Perhaps the most successful unit operating the Potez 631 was the Flottille F1C of the French Naval Air Arm; between 10-21 May 1940, aircraft of the unit shot down 12 enemy aircraft in exchange for 8 of its own losses prior to its withdrawal from active combat.[17]

At one point, the Potez 637 was the only modern aircraft equipping the Groupes de Reconnaissance (GOA), which had long been equipped with obsolete aircraft.[18] From November 1939 onwards, the first units to convert to the Potez P.63.11 were each assigned three aircraft. By mid-January 1940, there were 43 Potez 63.11s in service with 12 GOAs.[19] By June 1940, more than 700 reconnaissance Potez 63.11 had been delivered.[20] These aircraft encountered various fates in service, more than 220 were destroyed or abandoned; despite the addition of extra machine gun armament, aircraft having received either six, eight, or ten machine guns: the Potez 63.11 possessed the heaviest losses of any French type. One factor contributing to the high losses was the near-complete lack of spares, rending 70 per of all P.63.11 aircraft unserviceable even prior to the German invasion; many aircraft was destroyed on the ground by enemy bombing and strafing attacks, entire units were wiped out without conducting a single mission.[17]

The Potez 63.11 continued in service with the air force of Vichy France and within the forces of the Free French; this led to the two opposing sides operated the type in the North African theatre.[21] The Free French Air Force initially possessed as few as three Potez 630 aircraft, further models were captured from the Vichy French Air Force. The Germanys initially allowed several Potez 630-equipped units to continue under Vichy French control; these were typically stationed in Southern France and North Africa, in the latter theatre, they frequently engaged in combat with Allied forces.[22] By 1 November 1941, the Vichy Air Force had 22 Potez 630s, 82 Potez 631s, six Potex 637s, and 236 Potez 63.11 aircraft. Large numbers of Axis-aligned Potez 630s stationed in North Africa were destroyed by American bombers during Operation Torch; Allied 630s were also used during the operation to conduct ammunition supply missions and to respond to Luftwaffe aircraft.[22]

On 27 November 1942, German military units occupied Vichy Air Force bases and seized their aircraft, around 134 Potez 630s of several variants was taken.[22] Of the seized aircraft, 53 were refurbished and dispatched to Romania for use as trainers and target tugs; spare engines were also reused to power a number of LuftwaffeHenschel Hs 129Bs.[22] Production of the type was resumed under German control; significant numbers of aircraft appear to have been pressed into service by the Germans, mostly in liaison and training roles. The last three Potez 631s in service were recaptured examples; these made a final contribution following the cessation of hostility in their use as trainer aircraft at the Centre d'Essais en Vol for the revived French Air Force.[23]

Unlike many contemporary French aircraft, production of the Potez aircraft was reasonably prompt and the first deliveries were effected before the end of 1938. The 63 had been designed with mass production in mind and as a result, one Potez 630 was cheaper and faster to manufacture than one Morane-Saulnier M.S.406. As production tempo increased, a number of derivatives and experimental models were also developed.

A typical feature of the 630 and 631 was the frontal armament, which originally consisted in two 20 mm Hispano-Suiza HS.404 cannons in gondolas under the fuselage, though sometimes one of the cannons was replaced by a MAC 1934. Later in their career, 631s received four similar light machine guns in gondolas under the outer wings, though it was theoretically possible to fit six.

two-seater, light level bomber. The Potez 633 retained the fuselage, wings and engines of the 631 but the observer's position and cannon gondolas were deleted and a small bomb bay was added between the pilot and rear gunner. Front armament consisted of a single light machine gun in the nose. The bomb bay could house eight 50 kg-class or two 200 kg (440 lb) -class bombs. There was no bombardier position, as the rear gunner was supposed to direct the bombing run through a periscopic bombsight fitted ahead of him, a disposition that proved unworkable in the field.

Potez 633.01

The first two-seat bomber prototype flew in late 1937. The Armée de l'air ordered 133 Potez 633s in 1938, but two months later decided all aircraft in the light level bomber category should be 3-manned, like the Douglas DB-7 and Bloch MB.175. The French order for 633s was converted into an order for more 631s. The 633 was however offered for export and attracted orders from Romania, China and Greece.

Potez 632 Bp.2

One example of the dive bomber prototype was started, but completed as a 633 however with Hispano-Suiza engines. It was sold to Switzerland for evaluation.

Potez 639 AB2

The single two-seat attack bomber prototype was converted as a standard 633.

Dissatisfied with its strategic reconnaissance aircraft such as the troublesome Bloch MB.131, the Armée de l'air required the development of a derivative of the Potez 631 for this role.

Potez 637

Strategic reconnaissance aircraft. The observer was housed in a gondola under the fuselage; this arrangement resulted in an aircraft that retained most of the qualities of the 631. 60 examples were ordered in August 1938 and delivered.

At the same time, the Armée de l'Air was desperate to re-equip its army cooperation units which had particularly antiquated equipment, but since the development of the 637, had completely changed its mind about how the observer position should be arranged. Potez was therefore required to develop a variant that, while retaining the wings, engines and tail surfaces of the 631, hosted the observer in a more conventional nose glasshouse.

Potez 63.11

Because the pilot needed to be seated above the observer, the fuselage was taller, which resulted in degraded top speed and manoeuvrability. As a result the 63.11 proved very vulnerable, despite being protected with some armour and basic self-sealing coating over the fuel tanks. As a secondary light bomber capability was part of the requirements (though it was rarely if ever used), the fuselage accommodated a tiny bomb bay, carrying up to eight 10 kg-class bombs. This bomb bay was replaced by an additional fuel tank on late examples. Additionally, two 50 kg-class bombs could be carried on hardpoints under the inner wings. Frontal armament was originally one, then three MAC 1934s under the nose, and many 63.11s were equipped with the same additional guns in wing gondolas as the 631s.

The first Potez 63.11 No.1 and second No.2 prototypes first flew in December 1938, and no less than 1,365 examples were on order in September 1939, of which 730 were delivered, making the 63.11 the most numerous variant of the family by far.